Process of spinning viscose



Patented Dec. 11, 1951 PROCESS OF SPINNING VISCOSE Rudolph S. Bley, Milligan College, Tenn., assignor to North American Rayon Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application November 16, 1950, Serial No. 196,086

. 1 c In the manufacture and production of continuous ordiscontinuous multi-filament threads and yarn of relatively high tenacity from viscose, a viscose solution is extruded through the fine orifices of a spinneret into a coagulating bath containing sulphuric acid, zinc sulphate, and sodium sulphate, to form partially coagulated viscose filaments therein. The partially coagulated (partially regenerated) filaments are then immediately stretched while passing them through a dilute acid bath which contains less acid and salts than the aforesaid coagulating bath, and this second bath is maintained at a temperature above 60 C. This so-called "hot water spinning process, for example, is clearly disclosed in U. S. Patent No. 2,192,074, issued to Givens et al. on February. 27, 1940, and the present invention constitutes a carrying forward of this prior art process.

Although it has been found that the Givens et. al. process yields high quality products, nevertheless great difiiculties are experienced in practising the same due to the formation of hard zinc sulphide deposits on the walls of the troughs containing the hot dilute acid bath and on the guide rollers submerged therein. Furthermore the aforesaid zinc sulphide deposits cause clogging of the pipe lines through which the coagulating bath is recirculated for reasons of economy. Since the hard deposits on the guide rollers are especially detrimental due to their tendency to cut the filaments led thereover during their bath travel, it becomes necessary to resort to frequent cleaning and replacement of the guide rollers to counteract this serious trouble.

18 Claims. (Cl. 18-54) Investigation has shown that zinc sulphide deposits are formed by chemical interaction of zinc sulphate in the dilute coagulating bath with hyphates capable of forming soluble compounds in' the presence of sulphuric acid and having a sufficient stability therein at a temperature of above 60 C. Ammonium persulphate is preferred for 2 1 reasons of economy. Sodium persulphate may be prepared from sodium sulphate, crystallized from waste spin bath, by Well known electrolytic means, and used in this process.

Although in accordance with the present invention it is preferred to use persulphuric acid and soluble persulphates as oxidizing agents for reasons of efiiciency and economy, nevertheless these particular chemicals can be replaced by other Water-soluble oxidizing agents, namely inorganic and organic per acids and Water-soluble salts thereof, such as for example, peroxides, perborates, perchlorates, persilicates, percarbonates, permanganates, etc. I-Iypohalous acids and water-soluble salts thereof, suchas metal chlorites, bromites and iodites may serve also as suitable oxidizing agents for hydrogen sulphide and other unstable sulphur compounds produced during the regeneration of cellulose from cellulose xanthate (viscose). Since such sulphur compounds are oxidized in statu nascendi within the partially regenerated viscose filaments, fibers, films, etc., a considerable acceleration of the rate of regeneration of cellulose from viscose (cellulose xanthate) is obtained inherently by using this novel spinning process in addition to the inhibition of zinc sulphide deposits as set forth above. Obviously, the thread may be advanced through the succeeding spin baths in a straight or deviated path, or in the form of a helix having a plurality of loosely or closely spaced turns by means of suitable thread-storage, thread-advanc ing devices well known in the art of rayon manufacture, and by oxidizing the hydrogen sulphide in the primary and/or secondary hot bath, zinc sulphide deposits which would normally be formed on the walls of the tanks and the threadadvancing devices are inhibited. The viscose used for the production of relatively high tenacity yarn is prepared conventionally from rayon pulp containing more than alpha cellulose and about 0.1 to 0.6% lignin.

The aforesaid oxidizing agents react with hydrogen sulphide to form negatively charged, colloidal sulphur, and this sulphur does not form dense deposits on the walls of the spin bath troughs, the guide rollers, or in the pipe lines.

Moreover, the colloidal sulphur can be prevented from settling on the aforesaid surfaces by the addition of anion-active compounds to the hot, dilute coagulating bath. The anion-active compounds enhance the negative charge of the colloidal sulphur particles and thus keep the same in suspension. In other words, the colloidal sulphur particles are removed by flotation. Any

anion-active compound may be used for this purpose provided it is sufficiently stable at temperatures above 60 C. Examples of suitable anionactive compounds are sulphonated high-molecular alcohols, sulphonated hydrcxy benzenes having one or more straight chain alkyl groups having eight or more carbon atoms attached to the benzene nucleus, etc. such as soaps and products known commercially as aliphatic sulphonates, for example, sodium beta-oleylethanesulphonate, sodium beta-oleylamidoethanesulphonate, alkyl-. aryl sodium sulphonates of the type R.Ar.SO3Na in which the long-chain alkyl group is derived from petroleum, and sulphates of long-chain alcohols prepared by the hydrogenation of fats. About .1 to .5 gram of an anion-active compound are generally suiiicient per liter of bath to prevent the formation of loose sulphur deposits on the rollers submerged in the hot coagulating bath. The amount of persulphate ions to be provided in the hot coagulating bath depends upon the amount of hydrogen sulphide set free therein by the partially regenerated viscose filament, and can be readily determined by experiment. Generally speaking, about 3 grams per liter of bath are sufficient.

The primary acid coagulating bath contains sulphuric acid and also a sufficient amount of metallic sulphate to delay the decomposition of the viscose to cellulose hydrate. phate preferably employed is about 2.5 to 4% of zinc sulphatein addition to about 15 to 24% of sodium sulphate. The secondary, hot dilute acid coagulating bath contains less sulphuric acid and salts, and it ismaintained at a temperature of at least 60 C., and it is preferable to employ a temperature' of 80 C. or higher. The acid and salts for the dilute acid loath may be provided by acid and salts taken over by the filaments from the coagulating bath.

Example A normal viscose solution was extruded through a spinneret into a coagulating bath containing about 9.5% of sulphuric acid, 17.3% sodium sulphate, 4.9% magnesium sulphate, 2.8% zinc sulphate, and 65.5% water (all percentages calculated on the weight of the bath), to form a 480 filament, 1100' denier yarn. The yarn bundle was stretched in a dilute acid bath containing about 2 grams per liter of sulphuric acid, .97 gram per liter of zinc sulphate, and a total salt content of about 6.7 grams per liter, to which about 3 grams of ammonium persulphate were added per liter. The hot, dilute coagulating bath was maintained at a temperature of 85 C. Only a loose sulphur deposit was formed on the rollers submerged in this bath, and this deposit was completely inhibited by dissolving .5 gram per liter of an anion-active compound (an alkylaryl sodium sulphonate of the type R.Ar.SO3Na in which the long-chain alkyl' group is derived from petroleum) in'the persulphate bath. The yarn had a dry strength of 2.95 grams per denier, a wet strength of 1.72 grams per denier, 15% dry elongation, and 18% wet elongation. Similar results were obtained following the example set forth in the Givens patent, No. 2,192,074, when persulphate ions were provided in the hot, dilute acid coagulating bath. The process may also be modified by adding a persulphate to the primary and/or the secondary coagulating baths. The spinning process may be carried out with any other oxidizing agent set forth above in lieu of ammonium persulphate.

The process. may obviously be modified With- The metallic sulout departing from the spirit and scope of the invention as set forth in the appended claims.

This application is a continuation-in-part of my application Serial No. 727,947 filed Februa y 11, 1947, for Process of Spinning Viscose, now abandoned.

What is claimed is:

i. In a process for the manfacture and production of continuous or discontinous filaments of relatively high tenacity from viscose which includes partially regenerating the viscose filaments in a bath containing sulphuric acid and zinc and sodium sulphates wherein the proportion of the salts to the acid is such that immediate complete regeneration is prevented, then stretching the thus partially regenerated filaments with attendant reduction in cross-section and evolution of hydrogen sulphide while passing them through a dilute acid bath whichcontains less acid than the aforesaid bath and is maintained at a temperature above 60 0., which increases the plasticity of the partially decomposed cellulose xanthate filaments, the improvement which comprises providing said dilute acid bath with asufficient amount of a salt selected from the group consisting of ammonium persulphate, sodium persulphate and potassium persulphate to minimize the evolution of hydrogen sulphide therein, whereby the formation of zinc sulphide is inl h-ibited.

2. In a process for the manufacture and production of continuous or discontinuous filaments of relatively high tenacity from viscose which inciudes partially regenerating the viscose fila ments in a bath containing sulphuric acid and sodium sulphate and at least2.5% of zinc sulphate, the proportion of the said salts to the acid being such that immediate complete regeneration is prevented, then stretching the thus partially regenerated filaments with attendant reduction in cross-section and evolution of hydrogen sulphide while passing them through a dilute acid bath which contains less acid than the aforesaid bath and is maintained at a temperature above 5 60 Ct, which increases the plasticity of the partially decomposed cellulose xanthate filaments, the improvement which comprises providing said dilute acid bath with a sufiicient amount of a salt selected from the group consisting of ammonium persulphate, sodium persulphate and potassium persulphate to minimize the evolution of hydrogen sulphide therein, whereby the formation of zinc sulphide is inhibited.

3. In a process for themanufactureand production of continuous or discontinuous filaments of relatively high tenacity from viscose which includes partially regenerating the viscose filaments in a bath containing Sulphuric acid and zinc and sodium sulphates wherein the proportion of the salts to the acid is such that immediate complete regeneration is prevented, then stretching the thus partially regenerated fila ments with attendant reduction in cross-section and evolution of hydrogen sulphide while passing them through a dilute acid bath which containsless acid than the aforesaid bath and is maintained at a temperature above 60 C., which increase the plasticity of the partially decomposed cellulose xanthate filaments, the improvement which comprises providing said dilute acid path. with a sufiicient amount of a salt selected from. the group consisting of ammonium persulphate, sodium persulphateand. potassium persulphate to decompose the hydrogen sulphite evolved by said partially decomposed cellulose xanthate compound to maintain said filaments to form colloidal'sulphur 'and with a sufiicient amount of a dissolved anion-active sulphur in suspension. r a I 4. Process according to claim 1, in'which the acid and salts for the dilute acid bath are being provided by acid and salts taken over by the filaments from the coagulating bath.

5. Process according to claim 2, in which the acid and salts for the dilute acid bath are being provided by acid and salts taken over bythe filaments from the coagulating bath.

6. Process according to claim 3, in-which the acid and salts for thedilute acid bath are being provided by acid and salts taken over by the filaments from the coagulating bath.

7. In a :process for the manufacture and production of continuous or discontinuous filaments of relatively high tenacity from viscose which includes partially regenerating the viscose filaments in a bath containing sulphuric acid and zinc and sodium sulphates wherein the proportion of the salts to the acid is such that immediate complete regeneration is prevented, then stretching the thus partially regenerated filaments with attendant reduction in cross-section and evolution of hydrogen sulphide while passing them through a dilute acid bath which contains less acid than the aforesaid bath and is maintained at a temperature above 60 C., which increases the plasticity of the partially regenerated cellulose xanthate filaments, the improvement which comprises providing said dilute acid bath with a suflicient amount of ammonium persulphate to minimize the evolution of hydrogen sulphide therein, whereby the formation of zinc sulphide is inhibited.

8. In a process for the, manufacture and production of continuous ordiscontinuous filaments of relatively high tenacity from viscose which includes partially regenerating the viscose filaments in a bath containing sulphuric acid and sodium sulphate and at least 2.5% of zinc sulphate, the proportion of said salts to the acid being such that immediate complete regeneration is prevented, then stretching the thus partially regenerated filaments with attendant reduction in cross section and evolution of hydrogen sulphide while passing them through a dilute acid bath which contains less acid than the aforesaid bath and is maintained at a temperature above 60 C., which increases the plasticity of the partially decomposed cellulose xantl'iate filaments, the improvement which comprises providing said dilute acid bath with a sufficient amount of ammonium persulphate to minimize the evolution of hydrogen sulphide therein, whereby the formation of zinc sulphide is inhibited.

9. In a process for the manufacture and production of continuous or discontinuous filaments of relatively high tenacity from viscose which includes partially regenerating the viscose filaments in a bath containing sulphuric acid and zinc and sodium sulphate wherein the proportion of the salts to the acid is such that immediate complete regeneration is prevented, then stretching the thus partially regenerated filaments, with attendant reduction in cross-section and evolution of hydrogen sulphide while passing them through a dilute acid bath which contains less acid than the aforesaid bath and is maintained at a temperature above 60 C., which increases the plasticity of the partially decomposed cellulose iamhate filaments, the improvement which comprises providing said "dilute-acid-bath with a I sufficient amount of ammonium persulphate to decompose the hydrogen sulphide evolved by said partially decomposed xanthate filaments to form colloidal sulphur and with a sufiicient amount of a dissolved anion-active compound to maintain said sulphur in suspension. 1

10. A process according-to claim 7, in which the'acid and salts for the dilute acid bath are being provided by acid and. salts taken over by the. filaments from the coagulating bath.

11. A process according to claim 8, in which the acid and salts for the dilute acid bath are being providedv by acid and salts taken over by the filaments from the coagulating bath. 7

12. A process according to claim 9, in which the acid and salts for the dilute acid bath are being provided by acid and salts taken over by the filaments from the coagulating bath.

13. In a process for the manufacture and production of continuous or discontinuous filaments of relatively high tenacity from viscose which in cludes partially regenerating the viscose filaments in a bath containing sulphuric acid and zinc and sodium sulphates wherein the proportion of the salts to the'acid is such that immediate complete regeneration is prevented, then stretching the thus partially regenerated filaments with attendant reduction in cross-section and evolution of hydrogen sulphide. while passing them through a dilute acid bath which containsless acid than the aforesaid bath and is maintained at a temperature above 60 C., which increases the plasticity of the partially regenerated cellulose xanthate filaments, the improvement which comprises, providing said dilute acid bath with a. sufiicient amountof a metal persulphate to minimize theevolution of hydrogen sulphide therein, whereby the formation of zinc ments in a bath containing sulphuric acid and zinc and sodium sulphates wherein the proportion of the salts to the acid is such that immediate complete regeneration is prevented, then stretching the thus partially regenerated filaments with attendant reduction in cross-section and evolution of hydrogen sulphide while passing them through a dilute acid bath which contains less acid than the aforesaid bath and is maintained at a temperature above 60 C., which increases the plasticity of the partially regenerated cellulose xanthate filaments, the improvement which comprises providing said bath and said dilute acid bath with a sufiicient amount of a metal persulphate to minimize the evolution of hydrogen sulphide therein, whereby the formation of zinc sulphide is inhibited, said persulphate being dissolved in said bath and said dilute acid bath and bein sufliciently stable therein at a temperature of above 60 C.

15. In a process for the manufacture and production of continuous or discontinuous filaments of relatively high tenacity from viscose which includes partially regenerating the viscose filaments in a bath containing sulphuric acid and zinc and sodium sulphates wherein the proportion of the salts to the acid is such that immediate complete regeneration is prevented, then stretching the thus partially regenerated filaments with attendant reduction in cross-section and evolution. of hydrogen sulphide, while passing them through a dilute. acid bath which contains less acid than the aforesaid bath and is maintained at atemperature above 60 C., which increases the plasticity of the partially regenerated cellulose xanthate filaments, the improvement which comprises providing said bath and said dilute acid bath with a sufiicient amount of a persulphate selected from the group consisting of ammonium persulphate, sodium persulphate and potassium persulphate, whereby the formation of zinc sulphide is inhibited.

16. In a process for the manufacture and production of continuous or discontinuous filaments of relatively high tenacity from viscose which includes partially regenerating the viscose filaments in a bath containing sulphuric acid and zinc and sodium sulphates wherein the proportion of the salts to the acid is such that immediate complete regeneration is prevented, then stretching the thus partially regenerated filaments with attendant reduction in cross-section and evolution of hydrogen sulphide while passing them through a dilute acid bath which contains less acid than the. aforesaid bath and is maintained at a temperature above 60 C., which increases the plasticity of the partially decomposed cellulose xanthate filaments, the improvement which 7 comprises providing at least one of said acid baths with a. suflicient amount of an oxidizing agent to minimize the evolution of hydrogen sulphide' therein, whereby the formation of zinc sulphide is inhibited, said oxidizing agent being dissolved in said bath.

17. In a process for the manufacture and production of continuous or discontinuous filaments of relatively high tenacity from viscose which includes partially regenerating the viscose filaments in a bath containing sulphuric acid and sodium sulphate and at least 2.5% of zinc sulphate, the proportion of the said salts to the acid being such that immediate complete regeneration is prevented, then stretching the thus regenerated filamentswith attendant reduction in cross-section and evolution of hydrogen sulphide while passing them through a dilute acid bath which contains less acid than the aforesaid bath and is maintained at a temperature above 60 C., whichincreases the plasticity of the partially decomposed cellulose Xanthate filaw ments, the improvement which comprises providing at least one of said acid baths with a sufiicient amount of an oxidizing agent to minimize the evolution. of hydrogen sulphide therein, whereby the formation of zinc sulphide is inhibited, said oxidizing agent being dissolved in said bath.

18. In a process for the manufacture and production of continuous or discontinuous filaments of relatively high tenacity from viscose which includes partiall regenerating the viscose filaments in a bath containing sulphuric acid and zinc and sodium sulphates wherein the proportion of the salts to. the acid is such that immediate. complete regeneration is prevented, then stretching the thus regenerated filaments with attendant reduction in cross-section evolution of hydrogen sulphide While passing them through a dilute acid bath which contains less acid than the aforesaid bath and is maintained at a temperature above 60 (1., which increases the plasticity of the partially decomposed cellulose xanthate filaments, the improvement which comprises providing at least one of said acid baths with a sufficient amount of an oxidizing agent to decompose the hydrogen sulphide evolved by said partially decomposed cellulose xanthate filaments to form colloidal sulphur and with a sufiicient amount of an anion-active col. pound to maintain said surphur in suspension, said oxidizing agent and said anion-active compound being dissolved in said bath.

RUDOLPH S. BIEY.

No references cited. 

1. IN THE PROCESS FOR THE MANUFACTURE AND PRODUTION OF CONTINUOUS OR DISCONTINOUS FILAMENTTS OF RELATIVELY HIGH TENACITY FROM VISCOSE FILAMENTS CLUDES PARTIALLY REGENERATING THE VISCOSE FILAMENTS IN A BATH CONTAINING SULPHURIC ACID AND ZINC AND SODIUM SULPHATES WHEREIN THE PROPORTION OF THE SALTS OF THE ACID IS SUCH THAT IMMEDIATE COMPLETE REGENERATION IS PREVENTED, THEN STRETCHING THE THUS PARTIALLY REGENERATED FILAMENTS WITH ATTENDANT REDUCTION IN CROSS-SECTION AND EVOLUTION OF HYDROGEN SULPHIDE WHILE PASSING THEM THROUGH DILUTE ACID BATH WHICH CONTAINS LESS ACID THAN THE AFORESAID BATH AND IS MAINTAINED AT A TEMPERATURE ABOVE 60* C., WHICH INCREASES THE PLASTICITY OF THE PARTIALLY DECOMPOSED CELLULOSE XANTHATE FILAMENTS, THE IMPROVEMENT WHICH COMPRISES PROVIDING SAID DILUTE ACID BATH WITH A SUFFICINT AMOUNT OF SALT SELECTED FROM THE GROUP CONSISTING OF AMMONIUM PERSULPHATE, SODIUM PERSULPHATE AND POTASSIUM PERSULPHATE TO MINIMIZE THE EVOLUTION OF HYDROGEN SULPHIDE THEREIN, WHEREBY THE FORMATION OF ZINC SULPHIDE IS INHIBITED. 